An Experimental Study Of Simvastatin-collage Composite Sponge As A Direct Pulp Capping Material In Rat Molars

Objective:The simvastatin-collagen composite sponge as the direct pulp capping agent was applied to mechanical pulp exposure model of rat molars at the present study.The biological reaction of dental pulp and reparative dentin formation were observed.This study was aimed to assess the feasibility and efficacy of simvastatin-collagen composite sponge using as a new pulp capping material.Methods:Simvastatin-collagen composite sponge was prepared,and its property was tested by SEM.One hundred and twenty Sprague-Dawley rats were randomly divided into three groups: simvastatin-collagen composite sponge group(SIM group),collagen sponge group(CS group)and Ca(OH)2 group(CH group).Endodontic entry cavity was prepared on the occlusion of the first molars in left maxillary of each rat.And the contralateral teeth were used as normal control group.The rats were sacrificed at the time of 1,3,7,14,28 days.The first molars in maxillary of each rat were fixed.X-ray observation was carried out,then the specimens were taken to HE,Masson?s Thichroe staining and immunohistochemical staining after decalcified using EDTA.Dentin bridge formation and reaction of pulpal biology was evaluated histopathologically.Immunohistochemistry was used to detect the expression of BMP-2,VEGF in rat dental pulp after pulp capping.Results?1.SEM results: The simvastatin-collagen composite sponge is netlike and porous structure,and the size and distribution of its pores are uniform under the SEM.2.X-ray results: High density image could be seen in the site of pulp exposure in CH group on the 28 th day.In SIM group,it could be seen earlier at the time of 14 and 28 days,while in CS group,we could not observe any high density image in exposed area.3.HE and Masson?s Thichroe staining results: At different time point,different degrees of inflammation under the cavity were found in three groups.The inflammatory reaction in SIM group was lighter than the CH group,and it had statistical difference between SIM group and CH group on the 14 th day(P<0.05).The inflammatory reaction of the CS group was most serious among three groups.The degree of inflammatory reaction was significantly different between SIM group and CS group on the 14 th and 28 th day(P<0.01).During the observation period,SIM group induced the formation of reparative dentin much faster and better than other groups.As for dentin bridge formation,a significantly higher rate of complete bridge was observed for SIM group than CH and CS groups on the 14 th day(P<0.05),and for SIM and CH groups compared with CS group on the 28 th day(P<0.05).4.Immunohistochemical staining results: The normal pulp showed positive expression of VEGF in vascular endothelial cells,but the stain of BMP-2 was negative.The results of experimental group showed that VEGF and BMP-2 expression increased at first and then decreased after direct pulp capping.VEGF expression reached the peak on the 3th day.And the expression of BMP-2 was up to its maximum value on the 7th day.And the expression of VEGF,BMP-2 was mainly at the cytoplasm of vascular endothelial cells,fibroblasts,odontoblasts,neutrophils,etc.Expression of VEGF and BMP-2 in the experimental group were significantly higher than normal control group at the time of 1,3,7 and 14 days(P<0.01).The VEGF staining intensity in the SIM and CH groups were different from CS group on the 1th,3th and 7th day(P<0.05).The difference between SIM Results: group and CH group had an impact on the expression of VEGF on the 3th and 7th day(P<0.05).Simvastatin-collagen composite sponge and Ca(OH)2 enhanced more BMP-2 expression than collagen sponge on the 3th,7th and 14 th day(P<0.05).The difference of BMP-2 expression was significant on the 7th and 14 th day with the SIM and CH groups(P<0.05).Conclusion:1.Simvastatin-collagen composite sponge as a pulp capping material is low degree of inflammation reaction and good biocompatibility to pulp tissue.2.Simvastatin-collagen composite sponge induce reparative dentine much faster and better than Ca(OH)2.3.Simvastatin-collagen composite sponge can promote the repair of pulp injury,which may be related to induce the expression of VEGF and BMP-2 during pulp repair.In conclusion,simvastatin-collagen composite sponge exhibited good biocompatibility to pulp tissue and promoted the formation of reparative dentin.Simvastatin-collagen composite sponge as a pulp capping material has a good application prospect.